As wireless communications technologies evolve, wireless communications systems become increasingly sophisticated. Multi-mode and multi-band wireless systems are routinely available. Such systems may include circuit elements to support multiple modes, multiple frequency bands, or both. Typical multi-mode communications systems may communicate using at least one of two different modes of operation. The first mode, called half duplex, is a two-way mode of operation, in which a first transceiver communicates with a second transceiver; however, only one transceiver transmits at a time. Therefore, the transmitter and receiver in a transceiver do not operate simultaneously. For example, certain telemetry systems operate in a send-then-wait-for-reply manner. Many time division duplex (TDD) systems operate using a half duplex mode.
The second mode, called full duplex, is a simultaneous two-way mode of operation, in which a first transceiver communicates with a second transceiver, and both transceivers may transmit simultaneously; therefore, the transmitter and receiver in a transceiver must be capable of operating simultaneously. In a full duplex transceiver, signals from the transmitter must not interfere with signals received by the receiver; therefore, transmitted signals are at transmit frequencies that are different from received signals, which are at receive frequencies. Many frequency division duplex (FDD) systems operate using a full duplex mode.
As a result of the differences between full duplex operation and half duplex operation, RF front end circuitry may need specific circuitry for each mode. As a result, the RF front end circuitry may need separate signals for each mode. Additionally, support of multiple frequency bands may require specific circuitry for each frequency band or for certain groupings of frequency bands. As a result, the RF front end circuitry may need separate signals based on which frequency bands are in use. In order to reduce size and cost, and increase performance and efficiency, multi-mode and multi-band wireless systems need to support multiple modes, multiple bands, or both in a way to reduce size, cost, and insertion losses. Thus, there is a need for a wireless system that can effectively generate the separate signals needed for multi-mode operation, multi-band operation, or both.